A familiar Biblical phrase to which many non Christians cling is this: God is love, from 1 John 4.16. We might not know that the verses leading up to this simple statement are rich.
The chapter begins with the theme of the Spirit of God. John says test the spirits to see if they are from God. Among other things this implies that only one spirit comes to us from God, the Holy Spirit; He is sent as God to us. Any spirit must confess the Son, that Jesus has come from the Father, 1 John 4.2. And that's because only a spirit from God could do this. That's how we know to trust the spirit. Only the Spirit of God has experienced both the Son and the Father.
John says that we are from God, agreeing with Ephesians 1.4, and that God is in us, Ephesians 1.14. The spirits which are not from God are, from the world, 1 John 4.5, John 15.19. John says anyone with the Spirit living within them will listen to the apostles because the spirit of truth is in them, 1 John 4.6.
So we can see from the first 6 verses that the Spirit of God has come to us, He lives in our souls, and that He only can be trusted because He came from God, He did not come from the world. He witnesses to Jesus as the Son of God.
+++Now if the spirit of truth is in us, John says, let us love one another, for love is from God, 1 John 4.7, John 15.17. How do we know love is from God? Because of what God did, sending His Son. In the act of doing, love came forth, it was manifested. We know God loves us because He made Himself real to us in His Son. So if God has loved us, we should love one another. Notice John does not say return God's love to God--he says pass it on to one another. In the process of loving one another, God's Spirit will become apparent in us and among us.
This means, among other things, that the Spirit of God is His love.
Now we come to 1 John verse 12, a verse loaded with richness.
First John says, no one has beheld God at any time... So how would God ever be seen? John says He can be seen in us by others whom we love, if we love one another... This is because God abides in us, as He did in the tabernacle, and, His love is perfected in us. But how do we know that He abides in us, as we are loving one another? John's answer is, By this we know that we abide in Him and He in us, because He has given us of His Spirit, 4.13. There is the same thought, the Holy Spirit is God's love for us.
John saw and came to know not just that Jesus was the savior of the world, but that the Father sent Him. It is this confession that the Father has sent the Son to be the savior of the world which makes every follower a believer, 1 John 4.14. In other words, to be the Son is to be begotten of the Father and sent into the world. When we know this, we have God.
Those who are of the world, who do not confess that Jesus is the Son of God sent into the world by the Father, do not abide in the love of God. They can say, God is love, but the Holy Spirit will not abide in them if they do not confess that Jesus came from the Father as the Son of God. Verse 15 says it: Whoever confesses that Jesus is the Son of God, God abides in him and he in God.
Having said that only the spirit who confesses that Jesus is from the Father sent to us is true, and that we should love one another, how can we love in the perfection of the Holy Spirit?
First John says if God's Spirit is abiding in us,, God is abiding in us. As He is perfect, so His Spirit in us will be. Abiding is dwelling but it is not inert. We will experience the progress of the soul as we are in God. We will have no fear in love because perfect love casts out fear. This comes through experiencing God. When we receive the love which is from God, we will have no fear of judgment day, 4.17.
Second, this perfect love from God is also for today. John uses the example of loving our brother. We might recall the last phrase of Matthew 23.8: you are all brothers. Jesus had said to forgive your brother endlessly, Matt. 18.21, and if you have anything against your brother, be reconciled to him, Matt. 5.22, and don't be a hypocrite about your btother's sin, Matt. 7.4. So here, John says if you can't love your brother who stands in front of you, how can you love God whom you can't see, 1 John 4.20.
When we receive His Spirit, when we confess that Jesus is the Son of God coming to us, when we love one another as He has loved us, then the love of God is shed abroad in our hearts, one for another.
If you want to jump and shout, Halleleuiah, go ahead.